航空材料学报

2013, 33(3): .

[Abstract](1033) [PDF 274KB](245)

Abstract:

Creep Behavior of a Nickel-Based Single Crystal Superalloy

ZHANG Jian, ZHAO Yun-song, LUO Yu-shi, JIA Yu-liang, YANG Shuai, TANG Ding-zhong

2013, 33(3): 1-5.

[Abstract](1476) [PDF 1707KB](298)

Abstract:
A nickel-based single crystal superalloy was employed to study the high temperature creep under low applied stress behavior by using scanning electron microscope (SEM), transmission electron microscope (TEM) and some other research methods. The main results are summarized as follows: Initially, there existed a decreasing strain rate regime with the strain rate eventually reaching a minimum which occurs within the creep plateau. Thereafter the creep strain rate increased dramatically in what will be referred to as the increasing creep rate regime. The mechanism for primary creep is transverse glide of a/2〈110〉{111} dislocations in the matrix channels normal to the load axis. The mechanism for the steady creep is superlattice dislocation cutting ' precipitates, and the cutting dislocation is mainly composed of screw dislocation pair and [001] dislocation.

Structure and Properties of Sintering Body by Hot Isostatic Pressing Utilizing TC4 Hydrogenated Powder

TIAN Ya-qiang, HOU Hong-liang, REN Xue-ping

2013, 33(3): 6-11.

[Abstract](1371) [PDF 3204KB](242)

Abstract:
The effect of hydrogen content and processing parameters on structure and properties of TC4 alloy was researched by means of a new method to produce titanium alloy of combining hot isostatic pressing using hydrogenated powder and technology of hydrogen treatment for titanium alloy. The results show that with increasing of hydrogen content, the density of TC4 titanium sintered body gradually increases and the sheet microstructure gets thinner and finer and the grain size becomes smaller and isometric. After annealing, with hydrogen content increasing, the isometric grain of the TC4 titanium product increases, the compression yield limit and strength shows a gradually rising trend. The hydrogen content and the phase composition of the product by hot isostatic pressing are basically close to powder stock, and the safety status of hydrogen content of the product after annealing corresponding to the TC4 alloy state is achieved. The density and mechanical property of the TC4 titanium alloy are the best with the hydrogen mass fraction of 0.42%.

Microstructure and Mechanical Properties of Al-20Si-7.5Ni-3Cu-1 Mg-0.25Fe Alloy Prepared by Rapidly Solidified Powder Metallurgy

TANG Peng-jun, HE Xiao-lei, WANG Xing-yuan, LI Pei-yong

2013, 33(3): 12-17.

[Abstract](1368) [PDF 2002KB](245)

Abstract:
The Al-20Si-7.5Ni-3Cu-1Mg-0.25Fe alloy was prepared by rapidly solidified powder metallurgy process. The microstructures and mechanical properties of extruded and T6-treated alloys were investigated by OM, SEM, TEM, XRD and tensile test. The results show that both of the extruded and T6-treated alloys are constitutive of (Al), (Si), Al3Ni, Al3Ni2, Al7Cu4Ni and Al4Cu2Mg8Si7. The mean size of Si phases with sharp edges is 2.4m in the extruded alloy, while it is 3.2m in the T6 treated alloy after coarsening and spheroidizing. At room temperature, the ultimate tensile strength, yield strength and Rockwell hardness of T6-treated alloy reach up to 490MPa, 415MPa and 91.3HRB respectively. It has been found that the fracture surfaces of these alloys are flat and composed of small facets of Si phases, which indicate that the alloy fracture appearsed belongs to the brittle pattern.

Effects of Near-Isothermal Deformation Amounts on Microstructure Parameters and Tensile Properties of TC4-DT Titanium Alloy

PENG Xiao-na, GUO Hong-zhen, SHI Zhi-feng, QIN Chun, ZHAO Zhang-long

2013, 33(3): 18-24.

[Abstract](1308) [PDF 2533KB](254)

Abstract:
The influence of near-isothermal deformation amounts on microstructures and tensile properties of TC4-DT titanium alloy was studied by using optical microscope (OM), SEM, EPMA and metallurgical image-analysis software. Results showed that with the deformation amount increasing, grain boundary was changed from intact to broken up. Inside primary grain the size of coarse plate was increased and the width of acicular did not changed much. The formation of coarse plate was attributed to the element segregation induced by atom diffusion. At 60% deformation degree, atom diffusion was proceeded sufficiently which reduced the composition difference among different morphology and resulted in a homogeneous microstructure. The content and orientation of coarse varied with the increasing of deformation amounts. At low deformation degree (20%), the phase boundaries of / could not become the obstacle for dislocation gliding and this made the dislocation concentrated in grain boundary which led to intergranular fracture. While at higher deformation degree (60%), the orientation between and was disturbed, the phase boundaries of / became the obstacle for dislocation gliding which enhanced both strength and ductility, and tensile fractographs showed transgranular fracture. Conclusion has been obtained that a better combination of strength and plasticity can be reached at 60% deformation degree at this experiment condition.

Mechanical Behavior and Microstructure of TA15 Titanium Alloy during Hot Compressive Deformation

LI Cheng-ming, LI Ping, ZHAO Meng, XUE Ke-min

2013, 33(3): 25-29.

[Abstract](1414) [PDF 3269KB](247)

Abstract:
High temperature compression tests of TA15 titanium alloy were carried out on Gleeble-3500 simulator. The Experimental results include the true stress - true strain curves and microstructure transition of TA15 alloy under different process parameters,and the textures were investigated by electron backscattered electron diffracometry (EBSD). The results reveal that the flow stress decreases with deformation temperature rising and increases with strain rate growing. Strong textures are achieved and the main softening mechanism is dynamic recrystallization below transition, and dynamic recovery is in field.

Effect and Microscopic Mechanism of Shot Peening on Microstructure and Properties of 30CrMnSiNi2A Alloy Steel Surface Layer

LI Zhan-ming, ZHU You-li, XIE Jun-feng, DU Xiao-kun, CHEN Hai-feng, PAN Hong-hai

2013, 33(3): 30-33.

[Abstract](1399) [PDF 1394KB](258)

Abstract:
The strengthening treated samples of 30CrMnSiNi2A alloy steel were prepared by pneumatic shot peening equipments, and microstructure and mechanical properties of the samples surface layer were analyzed. Microstructures of the samples surface layer were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The surface layers’ hardness and residual stress distributions along the thickness direction of the samples with and without shot peening treatment were measured by nano-indention and X-ray diffraction method. The results showed that the organization of untreated sample is lath martensite and a small amount of bainite, twinning, and retained austenite. A plastic deformation layer was formed by the shot peening treatment, and the depth extended up to about 30 μm. The average grain size was about 46 nm in this layer which hardness average values was up to 6.83 GPa, and increased 4.9% than the untreated sample. At the same time, a residual compressive stress layer was also produced by shot peening treatment, and the depth was close to 300 μm. The maximum compressive residual stress was -1050 MPa. At last, the grain refinement mechanism of shot peening treatment and effect on work hardening, compressive residual stress were discussed.

Influence of Shot-Peening Coverage on Surface Integrity of TC4 Titanium Alloy

WANG Xin, LI Si-qing, MENG Zhen-wei, TANG Zhi-hui

2013, 33(3): 34-38.

[Abstract](1366) [PDF 1566KB](243)

Abstract:
TC4 titanium alloy was employed to investigate the effect of shot-peening coverage(SPC) on surface integrity, such as surface morphology, surface roughness, residual stress and microstructure after 200℃/1h heat treatment.The results show that the average roughness Ra, root-mean-square roughness Rq and the value of compressive residual stress increase with the rise of SPC. Dislocation movement and crystal self-coordinating are observed in 300% SPC after 200℃/1h heat treatment due to temperature and inner-stress, which causes the relaxation of residual stress, and more over, the relaxation is not observed in 100% SPC after 200℃/1h heat treatment.

Influence of Different Powder on Properties of WC-10Co-4Cr Coatings Prepared by HVOF

DIAO Wang-xun, WANG Zhi-xiong, GAO Jun-guo, WANG Chang-liang, GUO Meng-qiu, LIU Chao

2013, 33(3): 39-45.

[Abstract](1495) [PDF 3556KB](259)

Abstract:
The physical properties and phase composition of two different WC-10Co-4Cr powder prepared by kinds of sintering broken and agglomeration sintering processes were analyzed comparatively. Coatings were prepared by HVOF using the two powder and the properties of the two kinds of coatings were also evaluated comparatively. The results revealed that the hardness, porosity and erosion wear resistance of coating prepared from agglomeration sintering powder were superior to the coating from sintering broken powder. Nevertheless, the bonding strength of the coating from agglomeration sintering powder was appreciably lower than that from sintering broken powder.

Preparation and Tribological Properties of Self-Lubricating Al₂O₃/Graphite Composite Coating on TA2 Titanium

LI Wei-xue, ZHANG Kai, DAI Jian-feng, LIANG Jun, HUO Xiao-di

2013, 33(3): 46-52.

[Abstract](1352) [PDF 2937KB](237)

Abstract:
A graphite-containing Al2O3 composite coating on TA2 titanium was prepared by using one-step cathode plasma electrolytic deposition technology. The structure and composition of the ceramic coating was analyzed by SEM and XRD. In addition we analyzed the mechanism and process of the film formation. The tribological property of the coating was evaluated using friction testing. The results showed that the coating was composed of -Al2O3, -Al2O3 and graphite. The Al2O3-gaphite composite coating exhibited excellent self-lubricating behavior with lower friction coefficient and wear rate compared with TA2 titanium and graphite-free Al2O3 coating.

Low Cycle Fatigue Properties of Electron Beam Welded TC4 Titanium Alloy

LIU Xiao-hua, MA Ying-jie, LI Jin-wei, ZHANG Ren, LEI Jia-feng, LIU Yu-yin

2013, 33(3): 53-57.

[Abstract](1547) [PDF 2031KB](268)

Abstract:
Low cycle fatigue (LCF) properties of electron beam welded (EBW) TC4 alloy were tested and compared with base material (BM) under strain controlled condition. The LCF life of welded joint is obviously lower than that of BM under high t/2 condition,while equal under low t/2 condition, which was explained by the stress-strain loop and plastic feature of microstructure. The failure fracture occured in BM region, which was attributed to the relatively lower strength and weaker resistance to plastic diformation of BM region compared to the welded joint region. However, near surface crack initiated at the welded joint without further propagating due to high resistance to fatigue crack propagating from coarse grain microstructure.

Effect of Friction Stir Processing on the Microstructure of Cast Aluminum Alloy Applied to Plunger

LI Jing-yong, ZHUO Yan

2013, 33(3): 58-63.

[Abstract](1285) [PDF 2682KB](239)

Abstract:
The effects of friction stir processing (FSP) on the microstructure and micro-hardness of cast aluminum alloy ZL109 applied to plunger were investigated. Two kinds of stirring tools and different parameters were applied to process the cast aluminum alloy to improve the surface property. It is shown that under the action of mechanical stirring of tools, severe plastic deformation occurs in friction stir processing zones, and the larger crystalline grains of base metal were transformed into well-distributed equated fine grain, and fragmentized silicon particles were distributed on the aluminum matrix uniformly. Improper parameters of FSP bring out the grain growth in friction stir processing zones because of the exorbitant thermal effect. The average micro-hardness of friction stir processing zones was higher obviously than the average one of base material and the hardness distribution was more uniform.

Brazing Technology and Joint Properties of TA15 Titanium Alloy

HUAI Jun-feng, GUO Wan-lin, LI Tian-wen

2013, 33(3): 64-68.

[Abstract](1281) [PDF 1984KB](242)

Abstract:
TA15 is one kind of near- type titanium alloy with high aluminum equivalent, which possesses good hot stability the longtime working temperature up to 500℃. TA15 alloy was vacuum brazed with Ti-21Cu-13Zr-9Ni filler metal. The joint microstructure and element distribution of joint were analyzed by means of SEM and EDX , at the same time ,and the joint mechanical property testing was performed at the room temperature and high temperature. The results showed that the TA15 alloy brazed joint could be obtained by using Ti-21Cu-13Zr-9Ni filler metal. The joint tensile strength could be improved by post brazing diffusion treatment. At room temperature and 550℃, the joint tensile strength reached 98% and 94% of the base material respectively. For the specimens as brazed, brittle fracture was occurred in the joint, while for the specimens were diffusion treated after brazing, ductile fracture occurred in the base metal.

Shape Memory Effects of CTBN/CE Copolymers

NIU Lei, ZHU Guang-ming, WANG Kun, WEI Kun, SONG Rui

2013, 33(3): 69-73.

[Abstract](1394) [PDF 1192KB](279)

Abstract:
A novel shape memory resin system with high glass transition temperature(Tg) was prepared by the appropriate copolymerization of carboxy-terminated butadience acrylonitrile copolymer (CTBN) and cyanate ester (CE).This system was characterized by IR, dynamic mechanical analysis(DMA). And its shape memory properties, mechanical properties were also investigated. The results show that the block coplymer of proper content of CTBN and cyanate ester resin could exhibit excellent shape memory performance. The lowest Tg is in the temperature of 138℃, the largest deformation recovery rate of system is 100%, the maximum deformation recovery rate is 0.024 s-1; the maximum tensile deformation is 51%. And under the curing process of 120℃/2h+140℃/2h+160℃/2h+180℃/1h, the system tends to be completely cured.

Tension Mechanical Behavior of Two Angle-Ply of Glass-Fiber Reinforced Composites

ZENG Zhi, LI Yu-long, GUO Ya-zhou, CHEN Xuan, WANG Lei

2013, 33(3): 74-80.

[Abstract](1340) [PDF 1849KB](268)

Abstract:
Mechanical behavior of fiber reinforced composite (S4C9-1200/SY14, with two angle-ply of [0]16 and [45]4S) was investigated at strain rates ranging from 10-3s-1 to 103s-1 under uniaxial tension/compression by using an electronic universal testing machine and the Split Hopkinson Tension Bar (SHTB). Damage modes of this laminated composite are further examined, which can be clarified into fiber brittle rupture and fiber/matrix debonding, as well as its dependence on strain rate are studied. The experimental results show that disheveled catastrophic brittle failure is observed for the [0]16 specimens tested at quasi-static strain rates. For [45]4S specimens, the failure mode is mainly fiber/matrix debonding, and the damage is linear with the stress. Significant strain rate sensitivity is found for [45]4S specimens above strain rate value of the strengthen threshold.

Random Void Modeling for Carbon Fibre Reinforced Composite with Highly Dispersed Void Size

LIANG Xiang-yu, LIN Li, CHEN Jun, DING Shan-shan, LI Xi-meng

2013, 33(3): 81-85.

[Abstract](1381) [PDF 1494KB](224)

Abstract:
Based on the random void model (RVM) proposed upon random medium theory and statistical method, the modeling principles of porosity in carbon fiber reinforced composite were investigated. The porosities of the samples were 4.08% and 4.20% and the corresponding void length was in the range of 6.34-216.78m and 6.34-722.25m respectively.The voids were graded according to the length level. Model for each level was established. 2-D reconstructions were achieved by superposing models of all levels and compared with experimental micrographic results. It shows higher geometric similarity between the modeling results and the experimental results, which would provide valuable references for the future numerical calculations.

Out-of-Plane Mechanical Properties and Thickness Matching Optimization between Rib and Cell Thin-Wall of Reinforced Regular Hexagon Aluminum Honeycomb

WANG Zhong-gang, YAO Song

2013, 33(3): 86-91.

[Abstract](1268) [PDF 2127KB](231)

Abstract:
Based on explicit nonlinear finite element numerical simulation analysis method, series full-scale elaborator models of regular hexagon aluminum honeycomb with different geometric configurations reinforced with the same cell-wall thickness and ribs were constructed, and their mechanical properties impact at 10m/s were obtained. The comparisons between mechanical properties told out that the double-rib configuration is superior to the single-rib one, and the double-thickness configuration is superior to the single-thickness one. Afterwards, the thickness matching effect between rib and cell-wall was studied to word kinds of rib thickness combination. The influence of the rib thickness to the general buckling model was analyzed with equivalent apparent density index to evaluate the contribution of the deformation model change to the general mechanical properties. There is an obvious turning point, when the rib thickness smaller than that, the reinforced honeycomb performs a stably and perfectly at plateau stage, but with the increasing of the thickness, the response property changes abruptly with drastic waves. The load bearing capacity and energy-absorbing ability of the reinforced honeycomb with former proportion must drop. On the whole, the 1.5 times of the rib thickness to that of cell-wall is the most optimal option for reinforced honeycomb because of its excellent performance and significant promotion on plateau stress.

Ultra-high-cycle Fatigue Performance of a Titanium Alloy

ZHANG Hai-wei, HE Yu-ting, CHENG Li, GAO Chao, ZHANG Teng

2013, 33(3): 92-96.

[Abstract](1400) [PDF 1160KB](262)

Abstract:
Titanium alloy (TC17) specimens dimension and testing frequency were studied with the method of modal analysis and harmonic analysis of ANSYS software. Then, the specimens were implemented with 20kHz bending fatigue testing system to process ultra-high-cycle fatigue experiment at room temperature. The p-S-N curve was calculated based on testing results, and it shows that the traditional fatigue limit of the specimen does not exist while the fatigue cycles exceed 107. Paris model is used to calculate titanium alloy (TC17) specimens crack propagation life, which is under 2.1% of the median fatigue life.

2013 Vol. 33, No. 3